////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Jan Steemann
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_INDEXES_SORTED_INDEX_ATTRIBUTE_MATCHER_H
#define ARANGOD_INDEXES_SORTED_INDEX_ATTRIBUTE_MATCHER_H 1

#include "Basics/Common.h"
#include "Containers/HashSet.h"
#include "Indexes/Index.h"

namespace arangodb {
namespace aql {
class Ast;
struct AstNode;
class SortCondition;
struct Variable;
}  // namespace aql

class Index;

namespace SortedIndexAttributeMatcher {

Index::FilterCosts supportsFilterCondition(std::vector<std::shared_ptr<arangodb::Index>> const& allIndexes,
                                           arangodb::Index const* index,
                                           arangodb::aql::AstNode const* node,
                                           arangodb::aql::Variable const* reference, 
                                           size_t itemsInIndex);

Index::SortCosts supportsSortCondition(arangodb::Index const* index,
                                       arangodb::aql::SortCondition const* sortCondition,
                                       arangodb::aql::Variable const* reference, 
                                       size_t itemsInIndex);

/// @brief specializes the condition for use with the index
arangodb::aql::AstNode* specializeCondition(arangodb::Index const* index,
                                            arangodb::aql::AstNode* node,
                                            arangodb::aql::Variable const* reference);

/// @brief matches which index attributes of index are supported by the filter
/// condition represented by the passed-in AST node.
/// For example, if the query is 
///
///     FOR doc IN <collection-with-index> 
///       FILTER doc.value1 == 2 && doc.value2 == 3
///
/// then "reference" will point to the variable "doc" (this is the variable we are
/// looking for inside the filter condition(s). The filter condition will be an n-ary
/// AND consisting of the two sub-conditions "doc.value1 == 2" && "doc.value2 == 3".
/// the function will walk through all subconditions and will put the index attribute
/// that is used by the subcondition into the outvariable "found".
/// if a subcondition is not covered by the index, it will increase the counter 
/// "postFilterConditions", so the caller can see how many subconditions need to be
/// handled afterwards even when using the index. this is useful when comparing different
/// indexes, and to estimate the amount of post-filtering work left when picking a
/// particular index.
/// "values" is a counter variable and is increased by one for every equality condition,
/// and increased by the number of IN values for IN lookups. the counter is used to
/// estimate the number of items coming out of the index later.
/// while walking over the subconditions, the function will also populate "nonNullAttributes"
/// if it can prove a specific attribute for the search variable (e.g. "doc") cannot become
/// null. this can be useful later when looking at sparse indexes.
void matchAttributes(arangodb::Index const* index, arangodb::aql::AstNode const* node,
                     arangodb::aql::Variable const* reference,
                     std::unordered_map<size_t, std::vector<arangodb::aql::AstNode const*>>& found,
                     size_t& postFilterConditions, size_t& values, 
                     std::unordered_set<std::string>& nonNullAttributes, bool isExecution);

/// @brief whether or not the access fits
bool accessFitsIndex(
    arangodb::Index const* idx, arangodb::aql::AstNode const* access,
    arangodb::aql::AstNode const* other, arangodb::aql::AstNode const* op,
    arangodb::aql::Variable const* reference,
    std::unordered_map<size_t, std::vector<arangodb::aql::AstNode const*>>& found,
    std::unordered_set<std::string>& nonNullAttributes, bool isExecution);

bool isDuplicateOperator(arangodb::aql::AstNode const* node,
                         ::arangodb::containers::HashSet<int> const& operatorsFound);
};  // namespace SortedIndexAttributeMatcher

}  // namespace arangodb

#endif